IGBTs are well known devices having use in numerous switching applications. A typical IGBT and manufacturing process is described in British Patent 2,243,952 (GB IR-988). Two key characteristics of IGBTs are their forward voltage drop and their switching loss, both of which should be as low as possible. Thus, the forward voltage drop of a conventional IGBT formed in a silicon die is about 0.7 volts at the lowest. The switching speed of the device can be increased by the use of lifetime killing techniques such as irradiation, or the use of heavy metal doping, for example, gold and platinum, but this also increases its forward voltage drop.
Preferably, lifetime killing should be confined to the N.sup.+ buffer layer of the IGBT junction pattern. Further, it is desirable to have lifetime killing minority collection sites uniformly distributed within a desired predetermined volume within the device crystal lattice.